Bulletin 35 - July 1988: A Brief Survey of the Abu Dhabi Nature Reserve

A Brief Survey of the Abu Dhabi Nature Reserve

By Peter Hellyer

Introduction

The area of mangroves immediately to the east of Abu Dhabi Island (described at some length in ENHG Bulletin No.28, March 1986, by M.C. Crumbie) was declared a nature reserve in February 1987 by UAE President Sheikh Zayed bin Sultan al Nahyan, with the support of Crown Prince Sheikh Khalifa bin Zayed, following an approach by the Group’s Patron, University Chancellor Sheikh Nahyan bin Mubarak.

The initiative was taken at the Group’s prompting because of the area’s importance as a place for breeding birds an as a hatching ground for fish. Prior to the scheduling of this area a as reserve, it had been visited frequently not only by Group members but also by fishermen with nets, collectors of hone-combs, and persons on trail bikes or in four–wheel drive vehicles, who caused considerable damage to the young trees.

Once the area was declared a reserve, police stopped access. In January 1988 the Eastern Lagoon channel was extended except via a very circuitous route running past and through the precincts of the President’s palace. As a result, the area had been virtually undisturbed by human visits between February 1987 and April 22^nd 1988, when a brief three-hour survey of part of the reserve was permitted.

The survey was carried out at the request of President Sheikh Zayed, who sought information on the presence of Asian honeybees in the mangroves. The visit was facilitated by Sheikh Nahyan, who accompanied me on part of the survey, and who provided a small boat to cross the main channel.

Acknowledgements and thanks are due both to president Sheikh Zayed and to Sheikh Nahyan.

Apart from the search for honeybee colonies, the visit was designed to examine the current status of the Western Reef Heron heronry first described by M.C. Crumbie (see Crumbie 1986), and to identify any changes resulting the area’s new status as a reserve and from recent dredging work.

Changes in the Reserve Area since February 1987

The main physical change is the new channel, dredged to a depth of nine meters, which extends from the old sewage out fall at the end of the Eastern Lagoon to the smaller lagoon opposite the Qasr al Bahr (Beach Palace) of Sheikh Zayed. This is now the only route through which the tide ebbs and flows at all states of the tide, and the current is, consequently, fairly strong at times.

As a result there has already (within three months) been some erosion of the banks on either side of the channel, not only in the new part but also in the old dead-end of the Eastern Lagoon. Some small mangroves Avicennia marina and Arthrocnemum macrostachyum bushes have been undermined and have fallen into the water. However, the erosion of the banks is also creating a gentler slope, with the result that further erosion may be at a much slower pace. Areas of mangrove sapling growth near the new channel appear to be surviving satisfactorily.

The old channel for the tidal flow in and out of the Qasr al Bahr lagoon has become silted up at the end nearest to the Beach Palace, with the result that at low tides its entrance is completely dry. However, further down this old channel, which runs past the heronry of Western Reef Herons Egretta gularis (see below), there remains water of up to one meter deep at low tide, similar to that which existed prior to the establishment of the reserve. Little direct effect of the dredging could therefore be reserve. Little direct effect of the dredging could therefore be noted away from the main line of the newly extended channel.

In the heart of the mangroves themselves the only really significant change is that the previous signs for human intrusions have disappeared. The few tracks that ran between the trees have become partially overgrown, while the tire tracks across the mud caused by trail bikes have completely disappeared after fifteen months of daily tidal action.

There was no evidence of mangroves dying except in the big thicket with the heronry, and substantial new growth, both from seedlings and from shoots, was noted.

A quantity of driftwood brought in by the tide was scattered throughout the areas visited, while in the area nearest to he previous main point of entry some rubbish remained rusting in the undergrowth.

Asian Honey Bees

Three combs were noted, two relatively small, no more than eight to ten inches in diameter and roughly circular. These two, one of which was in an isolated bush and the other in the heronry, were both covered by swarms and could not be inspected closely. That in the bush was approximately four feet six inches off the ground, while that in the heronry was nine to ten feet above ground, while that in the heronry was nine to ten feet above ground level, in a tree of 15 to 20 feet in height.

The third comb was mature, much larger, approximately twelve inches across by 18 deep, and was still being used by only a small number of bees.

Breeding Birds

The heronry first recorded by M.C. Crumbie was inspected in part, following earlier observations from Abu Dhabi mainland that had shown Western Reef Herons taking up their usual perches on top of the trees.

In the small part inspected, about forty square, there were five occupied nests and one nest apparently dating from an earlier year. All were built of twigs in a fairly flimsy manner. One of the new nests, and the older one, were about six feet off the ground, while he others were eight to nine feet up in the trees. In each case there was a break in the tree canopy close to the nest, permit ease of access for the herons.

Eggs could be seen from the ground in all occupied nests, though the number of eggs in there was not ascertained. The other tow nests were examined closely. Each had three blue eggs side by side. On top of the mangrove shoots under the nest that was unoccupied, one freshly broken eggs hell was seen. The nest was examined but had not been in use, suggesting that the shell had been carried to the place by tidal action. Since it could have fallen from a nest, any assumption of chicks having hatched by the date of the visit is unwise.

Around ten Western Reef Herons were counted on an adjacent sandbank in the channel, clearly perturbed by my presence. However, since the whole heronry area was not visited, there may have been more nests. The number five above is a minimum figure.

Finally, it was noted that the mangrove shoots under the trees containing the heronry were very heavily encrusted with barnacles, much more so than in other less mature areas of the mangroves. It was not possible to determine whether this was because of the maturity of the trees, which have provided a suitable habitat for the barnacles for much longer, or because of the presence of more food because of the heronry. The number of small crabs seemed similar to that elsewhere.

Palm Dove (Streptopelia senegalensis)

Six nests were located, each with two eggs, one at a height of around three feet from the ground, the others at heights of six to eight feet. Incubating parents were noted no two of the nests. The species is a common resident and breeder.

Clamorous Reed Warbler (Acrocephalus stentoreus)

The typical call of this warbler was heard widely throughout the mangroves as usual, and two birds were seen. One was close t an isolated mangrove tree-which contained a newly made nest about five feet nine inches off the ground. It was tightly woven cup of grass and straw, with some very small twigs. No eggs were in the nest, but it was clearly very recently constructed since the bottom was clean and without rubbish like dead leaves, while the workmanship remained tight. A further visit to this probable breeding site has not been possible since.

Night Heron (Nycticorax nycticorax)

Two adult Night Herons were roosting in mangroves adjacent to the heronry and, when flushed, these flew around in a disturbed manner for up to two minutes before flying off over the trees. It was not possible to determine whether they also might have been breeding. They are not included in the Interim List of the Atlas of Breeding Birds of Arabia (ABBA), but can be seen in Abu Dhabi from mid-August round until mid-June.

Other bird species seen and identified during the visit:

Mallard – around 10, of which the majority were males. This duck has been recorded in the mangroves up to June, but breeding has never been proven in the UAE apart from a feral population in Dubai.

Graceful Warbler – two seen, acting in typically agitated fashion in a suitable nesting locality. Breeding has been previously recorded (see Crumbie, 1986).

Oystercatcher – 2

Grey Heron – 2

Redshank – 10+

Grey Plover – several, in both winter and summer plumage

Great White Egret – 1

Common Sandpiper – 1

Bar-tailed Godwit – 2

Kentish Plover – several, not far from proven breeding habitat on the far side of the channel (see Crumbie, 1986, and ENHG records for 1986, 1987 and 1988).

Curlew – a group of ten

A number of other smaller waders were not observed closely enough for positive identification.

Conclusion

The survey period, though brief, definitely confirmed the continued breeding status of Western Reef Herons and Palm Doves in the reserve, and showed that Graceful Warblers and Clamorous Reed Warblers remain probably breeders. Kentish Plovers have been recorded breeding during 1986 on the other side of the channel but could do so in the reserve only on the very few areas that are above the high tide mark, which were not visited.

The mangroves remain an important area for crustaceans, birds and for fish fry and, except along the outer rim, no damage appears to have been caused by the dredging of the new channel. On the contrary, the extra isolation of the reserve can only be beneficial, if inconvenient, for ENHG birdwatchers.

As Mammal Recorder for the Group, I should also record that no sign of mammals, domestic or otherwise, was noted during the visit. This is in contrast to the domestic cats and dogs that formerly visited the area before the cutting of the new channel.

A number of suitable sites for the construction of permanent hides can easily be identified, for the purpose of photography or simple bird recording, provided the necessary permission or access can be obtained.

Further (and scientific) study of the reserve is of considerable importance. The Group’s Patron, Sheikh Nahyan, has indicated his wish that the Desert and Marine Environment Research Center of the UAE University should undertake a study in due course, in association with the Group.